PluginBuilder

interface PluginBuilder

• config: BuildConfig & { plugins: BunPlugin[] }

  The config object passed to Bun.build as is. Can be mutated.

• module(

  specifier: string,

  callback: () => OnLoadResult | Promise<OnLoadResult>

  ): this;

  Create a lazy-loaded virtual module that can be imported or required from other modules

  @param specifier

  The module specifier to register the callback for

  @param callback

  The function to run when the module is imported or required

  @returns

  this for method chaining

  Bun.plugin({
    setup(builder) {
      builder.module("hello:world", () => {
        return { exports: { foo: "bar" }, loader: "object" };
      });
    },
  });
  
  // sometime later
  const { foo } = await import("hello:world");
  console.log(foo); // "bar"
  
  // or
  const { foo } = require("hello:world");
  console.log(foo); // "bar"
  
• onBeforeParse(

  constraints: PluginConstraints,

  callback: { external: unknown; napiModule: unknown; symbol: string }

  ): this;
• onLoad(

  constraints: PluginConstraints,

  callback: OnLoadCallback

  ): this;

  Register a callback to load imports with a specific import specifier

  @param constraints

  The constraints to apply the plugin to

  @param callback

  The callback to handle the import

  @returns

  this for method chaining

  Bun.plugin({
    setup(builder) {
      builder.onLoad({ filter: /^hello:world$/ }, (args) => {
        return { exports: { foo: "bar" }, loader: "object" };
      });
    },
  });
  
• onResolve(

  constraints: PluginConstraints,

  callback: OnResolveCallback

  ): this;

  Register a callback to resolve imports matching a filter and/or namespace

  @param constraints

  The constraints to apply the plugin to

  @param callback

  The callback to handle the import

  @returns

  this for method chaining

  Bun.plugin({
    setup(builder) {
      builder.onResolve({ filter: /^wat$/ }, (args) => {
        return { path: "/tmp/woah.js" };
      });
    },
  });
  
• onStart(

  callback: OnStartCallback

  ): this;

  Register a callback which will be invoked when bundling starts. When using hot module reloading, this is called at the start of each incremental rebuild.

  @returns

  this for method chaining

  Bun.plugin({
    setup(builder) {
      builder.onStart(() => {
        console.log("bundle just started!!")
      });
    },
  });